The wire mesh sensor (WMS) is currently among the most advanced instrumentation for high-resolution time-dependent two-phase flow measurements. So far, WMS have been applied to the analysis of mixing of liquids and to gas-liquid two phase flows. In this work, we show that a WMS can also be used for investigating the mass transfer from gas to liquid by measuring the soluble gas absorption in the liquid in the bubbly flow regime. Simultaneous measurement of the void fraction, bubble size, and interfacial area concentration of the gas, as well as the conductivity increase of the liquid due to CO₂ absorption allowed for the determination of CO₂ mass transfer from gas to liquid with a high spatial and time resolution.
In the experiments, the sensor was installed perpendicular to the flow in a small, 0.05 m x 0.05 m rectangular channel so that the measurement covered the whole cross-section area of the channel. A bubbly flow of pure, dry CO₂ with a superficial gas velocity in the range of 0.002-0.02 m/s was injected vertically upwards through a spherical orifice of 0.004 m in diameter to a pool of demineralized water. The pool height was approximately 1.57 m. Measurements were conducted at different heights in the channel to determine the evolution of the flow structure as well as the progressing absorption of the gas in the pool. Reference measurements were carried out with pure nitrogen as the gas phase to determine the size change of the bubbles due to CO₂ absorption along the vertical height of the water pool.
The liquid side mass transfer coefficient for CO₂ absorption in the water was determined based on simultaneous measurement of the CO₂ concentration in the liquid and the interfacial area concentration.